DOCSLIB.ORG

Revealing the Twohorns' of Taurus with GAIA

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Revealing the Twohorns' of Taurus with GAIA https://www.overleaf.com/project/5c86a42f0afdb00df4174248 Draft version January 30, 2020 Typeset using LATEX default style in AASTeX62 Revealing the Two `Horns' of Taurus with Gaia DR2 Graham D. Fleming,1 Jason M. Kirk,1 Derek Ward-Thompson,1 and Kate M. Pattle2, 3 1Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE, UK 2Institute for Astronomy and Department of Physics, National Tsing Hua University, No. 101, Section 2, Guangfu Road, Hsinchu 30013, Taiwan 3Centre for Astronomy, School of Physics, National University of Ireland Galway, University Road, Galway, Ireland Submitted to ApJ ABSTRACT We investigate the spatial properties of sources from the Gaia catalogue previously identified as being members of the Taurus star forming region and which appear in the Spitzer catalogue. We study an area of sky of 10◦×15◦, centred on Right Ascension (2000.0)=68.5◦ and Declination (2000.0)=27.0◦, this being an area surrounding the Taurus molecular cloud. We use data obtained from the Gaia DR2 release. By using an inversion of Gaia parallax measurements to obtain distance values and by defining limits to the proper motions of the Taurus moving group, we are able to show that there are substantial differences in depth within the Taurus complex. Our results suggest that the Taurus cloud has significant depth and that there are two main associations centred at ∼130±6 pc and ∼160±4 pc at 1σ. These two associations also have different proper motions, of 24.5±2.8 and 20.1±2.4 mas yr−1 respectively. We here label them the `Two Horns' of Taurus. Keywords: ISM: individual objects (Taurus molecular cloud) - stars: distances - parallaxes - proper motions 1. INTRODUCTION The Taurus molecular cloud (TMC) is one of the closest low-mass star-forming regions, lying at a commonly accepted distance of roughly 140 pc (Elias 1978). The region covers some 10 to 15 degrees in extent which equates to about 25 to 30 pc at this distance. This makes comprehensive studies of the entire stellar population of the region difficult and few comprehensive studies of the three-dimensional structure of the cloud complex have previously been conducted (e.g. Luhman 2018). Situated within the TMC are numerous filaments and smaller cloud structures (Hartmann 2002; Schmalzl et al. 2010; Kirk et al. 2013; Panopoulou et al. 2014; Marsh et al. 2016). Previous studies have shown that young stars are grouped in and around these smaller structures (Gomez et al. 1993; Kirk et al. 2013). Early distance measurements (McCuskey 1939) determined a distance of 142 pc to the Taurus star-forming region, whilst arXiv:1904.06980v3 [astro-ph.SR] 29 Jan 2020 later studies (Straizys & Meistas 1980; Meistas & Straizys 1981) of a number of Lynds dark clouds in the region (Lynds 1962) indicated that the TMC is more extended and exists between about 140 and 175 pc. +21 A study by Bertout et al.(1999) of three distinct regions of the complex placed the Lynds cloud L1495 at 125.6 −16 pc, +16 +42 the Auriga region at 140−13 pc, and the southern region at 168−28 pc. The investigation of early-type O and A stars located in the Taurus-Auriga molecular cloud (Mooley et al. 2013) within 1σ parallax error of 6.2< π <7.8 milli-arcsec (128 to 162 pc), identified a significant number of previously unidentified A5 or earlier stars within the region. Mooley et al.(2013) also noted in their study that even their new Corresponding author: Graham D. Fleming gdfl[email protected] 2 distribution fell far short of the expected number of such stars if a standard log-normal IMF distribution is assumed for the region, adding to the discussion previously noted by Goodwin et al.(2004) and other researchers (e.g. Kraus et al. 2017). In their study, Bertout & Genova(2006) derived kinematic parallaxes of 67 members of the Taurus moving group +42 with typical errors of 20% and identified weak-line and classical T Tauri stars spread over distances between 106−24 +61 and 259−42 pc. Very Long Baseline Array (VLBA) parallax observations of the Taurus star-forming regions conducted by Torres et al.(2007, 2009) showed a difference in the distances to separate regions of the Taurus complex by studying a small sample of individual sources. They noted a distance of 161.2±0.9 pc for the star HP Tau/G2 and 146±0.6 pc for T Tau (from Loinard et al.(2007)) in the eastern part of the complex, and 130 pc to the central area of the star-forming complex, by observing the T Tau-type stars Hubble 4 (V* V1023 Tau) at 132±0.5 pc and HDE 283572 at 128.5±0.6 pc. A multi-wavelength photometric study of the Taurus region Gudel et al.(2007) using Spitzer and XMM- Newton data produced large-scale maps detailing the stellar and substellar distribution of the region, and in a similar survey of the TMC conducted by Rebull et al.(2010), pre-main sequence members of the Taurus molecular clouds were identified using the Spitzer Space Telescope Taurus project (SSTtau) catalogue (http://cds.u-strasbg.fr/cgi- bin/Dic-Simbad?SSTtau) and Two-Micron All-Sky Survey (2MASS) data (http://vizier.u-strasbg.fr/cgi-bin/VizieR?- source=B/2mass). In other, more recent research, planetary-mass brown dwarfs in the Taurus and Perseus star-forming regions have been investigated using photometric and proper motion data from a number of space and ground-based platforms including Spitzer and Gaia DR1 (Esplin & Luhman 2017). Galli et al.(2018) presents trigonometric parallax and proper motion observations of Young Stellar Objects (YSOs) in the Taurus region as part of the Gould Belt Distances Survey using the VLBA. Their data suggest a significant difference between the closest and farthest stars in their sample of about 36 pc with the closest lying at 126.6±1.7 and the most distant at 162.7±0.8 pc. Within this range they noted that the central portion of the L1495 dark cloud is at 129.5±0.3 pc, whilst the supposedly associated B216 structure lies at 158.1±1.2 pc. The more recent comparison of Gaia DR2 and VLBI astrometry results (Galli et al. 2019) revise these distances but again confirm the existance of significant depth effects within the TMC. Contemporary studies of the TMC using Gaia DR2 data conducted by (Luhman 2018; Esplin & Luhman 2019), present comprehensive studies of the stellar membership of the Taurus region. In both studies extensive reference is made to earlier works with regard to the stellar membership of specific cloud complexes within the TMC and the kinematics of their members. No evidence for an older population of stars previously identified by Kraus et al.(2017) and Zhang et al.(2018) is found, however the existence of a possible moving group of stars at a distance of 116 to 127 pc with ages of ∼40 Myr first identified in the Gaia DR1 data by Oh et al.(2017) is suggested. Previous studies such as those listed above have identified significant distance dispersion among the stellar members of various regions within the TMC star-forming complex, and have further suggested considerable depth effects within the cloud. In contrast to more recent studies, we revisit the coherent catalogue of sources identified by Rebull et al. (2010) in the Spitzer SSTtau catalogue and use the newly available data from Gaia data release 2 to model the characteristics and detailed internal distribution of sources within the region as a whole (Brown et al. 2018; Luhman 2018). Where our studies overlap, we note that our findings are consistent with those of Luhman(2018) and Galli et al.(2019) and consider them complementary to the results of these studies. Section2 provides a brief overview of the Gaia mission and some of the relevant issues concerning DR2. The acquisition of data and its subsequent analysis are discussed in x3 with particular attention being paid to the statistical treatment of the data. Section4 presents a discussion of our data which is briefly summarised in x5. A compendium of the sources discussed in this study are presented in the Appendix. 2. GAIA The European Space Agency Gaia astrometric space observatory (Lindegren & Perryman 1996) was launched in December 2013. The spacecraft is designed to measure the parallax, positions and proper motions of stars, with the ambitious goal of producing a three-dimensional map of most of our Galaxy. Gaia is not designed to measure distances directly, but they can be inferred through the determination of stellar parallax. The Gaia Archive1 is a relational database which can be accessed through an interactive user interface and interrogated using conditional queries. 1 http://gea.esac.esa.int/archive/ 3 The second Gaia data release (DR2) occurred in April 2018 with a five-parameter astrometric solution for more than 1.33×109 sources (Brown et al. 2018). DR2 parallax uncertainties are in the range of up to 0.04 milli-arcseconds (mas) for sources with a broad-band, white-light magnitude (G) <15 and in the order of 0.7 mas at G=20. Coupled with proper motion measurements from DR2, a detailed investigation of the internal kinematics of the Taurus star-forming region can be made. Due to the relative proximity of the Taurus star-forming region, where the parallaxes are positive and relative uncertainties are small, a Bayesian prior is not employed in this study (Bailer-Jones 2015; Bailer-Jones et al. 2018; Luri et al. 2018), and a straightforward inversion of parallax is used to infer distance.
Load more

Recommended publications
  • 1 the XMM-NEWTON SURVEY of the TAURUS MOLECULAR CLOUD: ACCRETION, JETS, and FLUORESCENCE M. Audard1, Manuel Güdel2, Kevin Brigg
    1 THE XMM-NEWTON SURVEY OF THE TAURUS MOLECULAR CLOUD: ACCRETION, JETS, AND FLUORESCENCE M. Audard1, Manuel G¨udel2, Kevin Briggs2, and the XEST Team3 1Columbia Astrophysics Laboratory, 550 West 120th Street, NC 5247, New York, NY 10027, USA 2Paul Scherrer Institut, 5232 Villigen PSI, Switzerland ABSTRACT 1031 The Taurus Molecular Cloud (TMC) is one of the best studied star forming regions. It is close (140 pc) and represents the mode of isolated, non-clustered star for- mation. XMM-Newton has surveyed the richer 5 square degrees of the TMC in X-rays and has obtained high- 30 quality photometric and spectroscopic data of young stars 10 LX and brown dwarfs in their early stages of formation. We present results of the X-ray Emission Survey of TMC (XEST) on the following topics: i) Accretion. The ori- gin of X-rays in young, accreting stars is controversial, as accretion appears to be the dominant emission mech- 1029 anism in some classical T Tauri stars, whereas magnetic activity is the preferred explanation for others. The TMC 10-10 10-9 10-8 10-7 10-6 10-5 Mdot contains several accreting stars whose spectra help us un- derstand the importance of accretion for the production of X-rays. ii) Jets. Young, accreting stars display jets detected in the optical, near-infrared, and radio domains. There is now evidencethat jets are also detected in X-rays in some TMC targets. iii) Fluorescence. The detection of 7.5 an emission feature at 6.4 keV indicates that fluorescence of Fe in a cool environment,e.g., the accretion disk, takes place due to photoionization by hard X-rays or collisions logTav with electron beams.
    [Show full text]
  • Statistics of Superimposed Flares in the Taurus Molecular Cloud
    A&A 468, 477–484 (2007) Astronomy DOI: 10.1051/0004-6361:20066551 & c ESO 2007 Astrophysics The XMM-Newton extended survey of the Taurus molecular cloud Special feature Statistics of superimposed flares in the Taurus molecular cloud K. Arzner1, M. Güdel1, K. Briggs1, A. Telleschi1, and M. Audard2, 1 Paul Scherrer Institut, CH 5232 Villigen, Switzerland e-mail: [email protected] 2 Columbia Astrophysics Laboratory, 550 West 120th St., MC 5247, New York, NY 10027, USA Received 12 October 2006 / Accepted 19 February 2007 ABSTRACT Context. Stochastically occurring flares provide a possible mechanism of coronal heating in magnetically active stars such as T Tauri objects in star-forming regions. Aims. We investigate the statistics of stellar X-ray light curves from the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). Methods. To this end, the light curve is modeled as superimposed flares occurring at random times and with random amplitudes. The flare shape is estimated non-parametrically from the observations, while the flare amplitude distribution is modeled as a truncated power law, and the flare times are assumed as uniformly distributed. From these model assumptions, predictions on the binned counts are derived and compared with the observations. Results. From a sample of 22 XEST observations matching the above model assumptions we find that the majority of cases have flare amplitude distributions with slopes steeper than two. This favours the role of small flares in coronal heating for 5 targets, of which, however, 4 are foreground or background main-sequence stars. Key words. methods: statistical – stars: coronae – stars: pre-main sequence – X-rays: stars 1.
    [Show full text]
  • Protostars and Planets V
    Protostars and Planets V Hilton Waikoloa Grand Ballroom Oral Program Speakers are listed in italics MONDAY October 24, 2005 6:45 a.m. - 8:00 a.m. Breakfast and Posters Chair morning session: Ewine van Dishoeck 8:00 a.m. - 8:15 a.m. Welcome I. CLOUDS AND CORES 8:15 a.m. - 8:50 a.m. Giant Molecular Clouds in Galaxies Leo Blitz, Yasuo Fukui, Akiko Kawamura, Adam Leroy, Norikazu Mizuno, Erik Rosolowsky 8:50 a.m. - 9:25 a.m. Near-Infrared Extinction and the Structure and Nature of Molecular Clouds Charles J. Lada, Joao F. Alves, Marco Lombardi, and Elizabeth A. Lada 9:25 a.m. - 10:00 a.m. Molecular Cloud Turbulence and Star Formation Javier Ballesteros-Paredes, Ralf S. Klessen, Mordecai-M. Mac Low, Enrique Vazquez-Semadeni 10:00 a.m. - 10:30 a.m. Break and Posters 10:30 a.m. - 11:05 a.m. Structure and Evolution of Low Mass Dense Cores: An Observational Perspective James Di Francesco, Philippe Andre´, Derek Ward-Thompson, Paola Caselli, Mario Tafalla, Philip C. Myers, Neal J. Evans, Yancy L. Shirley, Yuri Aikawa, Doug Johnstone, Richard M. Crutcher, Christine D. Wilson, and Toshikazu Onishi 11:05 a.m. - 11:40 a.m. Extreme Deuteration and Hot Corinos: The Earliest Signatures of Low-Mass Star Formation Cecilia Ceccarelli, Paola Caselli, Xander Tielens, Eric Herbst, and Emmanuel Caux 1 II. STAR FORMATION AND PROTOSTARS 11:40 a.m. - 12:15 p.m. Current Advances in the Computational Simulation of the Formation of Low-Mass Stars Richard I. Klein, Shu-ichiro Inutsuka, Paolo Padoan, Kohji Tomisaka 12:15 p.m.
    [Show full text]
  • X-Ray Super-Flares from Pre-Main Sequence Stars: Flare Energetics and Frequency
    Draft version May 12, 2021 Typeset using LATEX twocolumn style in AASTeX63 X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency Konstantin V. Getman1 and Eric D. Feigelson1, 2 1Department of Astronomy & Astrophysics Pennsylvania State University 525 Davey Laboratory University Park, PA 16802, USA 2Center for Exoplanetary and Habitable Worlds (Accepted for publication in ApJ, May 2021) ABSTRACT Solar-type stars exhibit their highest levels of magnetic activity during their early convective pre- main sequence (PMS) phase of evolution. The most powerful PMS flares, super-flares and mega-flares, −1 have peak X-ray luminosities of log(LX ) = 30:5−34:0 erg s and total energies log(EX ) = 34−38 erg. Among > 24; 000 X-ray selected young (t . 5 Myr) members of 40 nearby star-forming regions from our earlier Chandra MYStIX and SFiNCs surveys, we identify and analyze a well-defined sample of 1,086 X-ray super-flares and mega-flares, the largest sample ever studied. Most are considerably more powerful than optical/X-ray super-flares detected on main sequence stars. This study presents energy estimates of these X-ray flares and the properties of their host stars. These events are produced by young stars of all masses over evolutionary stages ranging from protostars to diskless stars, with the occurrence rate positively correlated with stellar mass. Flare properties are indistinguishable for disk- bearing and diskless stars indicating star-disk magnetic fields are not involved. A slope α ' 2 in the −α flare energy distributions dN=dEX / EX is consistent with those of optical/X-ray flaring from older stars and the Sun.
    [Show full text]
  • Arxiv:2105.09338V2 [Astro-Ph.GA] 16 Jun 2021
    Draft version June 18, 2021 Typeset using LATEX twocolumn style in AASTeX63 Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories Ronan Kerr,1 Aaron C. Rizzuto,1, ∗ Adam L. Kraus,1 and Stella S. R. Offner1 1Department of Astronomy, University of Texas at Austin 2515 Speedway, Stop C1400 Austin, Texas, USA 78712-1205 (Accepted May 16, 2021) ABSTRACT Young stellar associations hold a star formation record that can persist for millions of years, revealing the progression of star formation long after the dispersal of the natal cloud. To identify nearby young stellar populations that trace this progression, we have designed a comprehensive framework for the identification of young stars, and use it to identify ∼3×104 candidate young stars within a distance of 333 pc using Gaia DR2. Applying the HDBSCAN clustering algorithm to this sample, we identify 27 top-level groups, nearly half of which have little to no presence in previous literature. Ten of these groups have visible substructure, including notable young associations such as Orion, Perseus, Taurus, and Sco-Cen. We provide a complete subclustering analysis on all groups with substructure, using age estimates to reveal each region's star formation history. The patterns we reveal include an apparent star formation origin for Sco-Cen along a semicircular arc, as well as clear evidence for sequential star formation moving away from that arc with a propagation speed of ∼4 km s−1 (∼4 pc Myr−1). We also identify earlier bursts of star formation in Perseus and Taurus that predate current, kinematically identical active star-forming events, suggesting that the mechanisms that collect gas can spark multiple generations of star formation, punctuated by gas dispersal and cloud regrowth.
    [Show full text]
  • Subaru Coronagraphic Search for Companion Brown Dwarfs
    Brown Dwarfs fA U Symposium, Vol. 211, 2003 E. L. Martin, ed. Subaru Coronagraphic Search for Companion Brown Dwarfs 1 Yoichi Itoh , Motohide Tamura/', Saeko S. Hayashif, Yumiko Oasa", 2 4 Misato Fukagawa", Hiroshi Sut0 , Koji Murakawa'", Takahiro Naoi 1 Graduate School of Science f3 Technology, Kobe University 1-1 Rokkodai, Nada, Kobe, Hyogo 657-8501, Japan, [email protected] 2 National Astronomical Observatory of Japan 3 National Space Development Agency of Japan 4 University of Tokyo Abstract. Near-infrared coronagraphic images of GG Tau and GK Tau are presented as preliminary results of the search for young brown dwarfs around T Tauri stars. 1. Introduction We are now conducting a near-infrared coronagraphic search for young brown dwarfs around T Tauri stars in the Taurus molecular cloud. The reasons why the study is aimed at such objects are as follows. 1) Brown dwarfs are orders of magnitudes brighter in the young stage than in the mature stage. In a binary system, the magnitude difference is smaller in the young stage than in the mature stage; 2) The binary frequency of objects associated with the Taurus molecular cloud is greater than those of the main-sequence stars by at least a factor of 2. However, young brown dwarfs are thought to be still very faint, therefore we need to conduct observations with a large aperture telescope. Moreover, young brown dwarfs as companions are thought to be in close vicinity of the bright central object, therefore we need observations with a high dynamic range as well as high spatial resolution.
    [Show full text]
  • THE STAR FORMATION NEWSLETTER an Electronic Publication Dedicated to Early Stellar Evolution and Molecular Clouds
    THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar evolution and molecular clouds No. 45 — 14 June 1996 Editor: Bo Reipurth ([email protected]) Abstracts of recently accepted papers High spatial resolution ‘shift-and-add’ imaging at UKIRT: multiplicity amongst YSO’s C. Aspin1,2, P.J. Puxley3, T.G. Hawarden1, M.J. Paterson3, and D.A. Pickup3 1 Joint Astronomy Centre, 660 N. A’Ohoku Place, Hilo HI 96720 U.S.A. 2 Nordic Optical Telescope, Apartado 474, E38700 Santa Cruz de la Palma, Canarias, Spain 3 Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ. Scotland E-mail contact: [email protected] We present results from near-IR ‘shift-and-add’ imaging on the UKIRT using the upgraded near-IR imaging camera, IRCAM3, and new control electronics, ALICE. Commissioning data on 12 sources in the Ophiuchus dark cloud complex are described. All but one source have previously been studied using 2D speckle imaging. We compare the results obtained by the two techniques and demonstrate that ‘shift-and-add’ imaging with IRCAM3 can produce results comparable to those obtained by 2D speckle technique. We additionally discuss both the current imaging quality of the UKIRT and its predicted performance after the planned thermal, dynamical and optical upgrades. Accepted by MNRAS Preprint at http://www.not.iac.es/∼caa/caa papers.html The Environment of V633 Cas and V376 Cas: Evidence for Circumstellar Disks Louis Asselin1, Fran¸coisM´enard2, Pierre Bastien1, Jean-Louis Monin2, and Daniel Rouan3 1 Observatoire du mont M´egantic et D´epartement de physique, Universit´ede Montr´eal,B.
    [Show full text]
  • 1 from Molecular Clouds to the Origin of Life
    1 From Molecular Clouds to the Origin of Life Pascale Ehrenfreund and Karl M. Menten In our Milky Way and in external galaxies, the space between the stars is filled with an interstellar medium (ISM) consisting of gas and dust. The ISM can be divided in vari- ous different components with very different physical parameters, ranging from a very hot (106 K), dilute (<10-2 particles cm-3) component heated by supernova explosions, which fills more than half of its volume, to molecular clouds with temperatures from 8 10 to 100 K and molecular hydrogen (H2) densities from a few hundred to 10 parti- cles cm-3, which make up less than 1% of the ISM's volume. Approximately 1% of its mass is contained in microscopic (micron-sized) interstellar dust. While accounting for only a small fraction (~1%) of the Galaxy's mass, the ISM is nevertheless an important part of the Galactic ecosystem. Gravitational collapse of dense interstellar clouds leads to the formation of new stars, which produce heavier elements in their interiors by nucleosynthesis. The main reaction in stellar interiors is the nuclear fusion of H into He. In a later stage of stellar evolution C, N and O are formed. Further nucleosynthesis occurs in massive stars leading to elements as heavy as iron. At the end of their lifetime which is mainly determined by their initial mass, stars return material to the interstellar environment by mass outflows, forming ex- panding shells and envelopes, as well as by violent explosions. Thus, the ISM repre- sents an environment, in which atoms, molecules, and solid matter undergo strong evolution and recycling.
    [Show full text]
  • Arxiv:2006.01326V1 [Astro-Ph.GA] 2 Jun 2020 58090 Morelia, Michoacan, Mexico
    Noname manuscript No. (will be inserted by the editor) From diffuse gas to dense molecular cloud cores Javier Ballesteros-Paredes · Philippe Andre,´ · Patrick Hennebelle, · Ralf S. Klessen, · Shu-ichiro Inutsuka, · J. M. Diederik Kruijssen, · Melanie´ Chevance, · Fumitaka Nakamura, · Angela Adamo · Enrique Vazquez-Semadeni Received: 2020-01-31 / Accepted: 2020-05-17 Abstract Molecular clouds are a fundamental ingredient of galaxies: they are the channels that transform the diffuse gas into stars. The detailed process of how they Javier Ballesteros-Paredes Instituto de Radioastronom´ıa y Astrof´ısica, UNAM, Campus Morelia, Antigua Carretera a Patzcuaro 8701. 58090 Morelia, Michoacan, Mexico. E-mail: [email protected] Philippe Andre´ Laboratoire d’Astrophysique (AIM), CEA/DRF, CNRS, Universite´ Paris-Saclay, Universite´ Paris Diderot, Sorbonne Paris Cite,91191´ Gif-sur-Yvette, France Patrick Hennebelle AIM, CEA, CNRS, Universite´ Paris-Saclay, Universite´ Paris Diderot, Sorbonne Paris Cite,´ 91191, Gif- sur-Yvette, France Ralf S. Klessen Universitat¨ Heidelberg, Zentrum fur¨ Astronomie, Institut fur¨ Theoretische Astrophysik, Albert-Ueberle- Str. 2, 69120 Heidelberg, Germany, Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan J. M. Diederik Kruijssen Astronomisches Rechen-Institut, Zentrum fur¨ Astronomie der Universitat¨ Heidelberg, Monchhofstraße¨ 12- 14, 69120 Heidelberg, Germany, Melanie´ Chevance Astronomisches Rechen-Institut, Zentrum fur¨ Astronomie der Universitat¨ Heidelberg,
    [Show full text]
  • Large Water Reservoirs at the Dawn of Stellar Birth 9 October 2012
    Large water reservoirs at the dawn of stellar birth 9 October 2012 More than 2000 Earth oceans-worth of water vapour were detected, liberated from icy dust grains by high-energy cosmic rays passing through the cloud. Herschel's infrared view of part of the Taurus Molecular Cloud, within which the bright, cold pre-stellar cloud L1544 can be seen at the lower left. It is surrounded by many other clouds of gas and dust of varying density. The Taurus Molecular Cloud is about 450 light-years from Earth and is the nearest large region of star formation. The image covers a field of view of approximately 1 x 2 arcminutes. Credit: ESA/Herschel/SPIRE (Phys.org)—ESA's Herschel space observatory has Close-up of L1544 with the water spectrum seen by discovered enough water vapour to fill Earth's Herschel, taken from the centre of the pre-stellar core. oceans more than 2000 times over, in a gas and The peak of the graph shows an excess in brightness, or dust cloud that is on the verge of collapsing into a emission, while the trough shows a deficit, or absorption. new Sun-like star. These characteristics are used to indicate the density and motions of the water molecules within the cloud. Stars form within cold, dark clouds of gas and dust Emission arises from molecules that are approaching the centre where the new star will form, from the back of the – 'pre-stellar cores' – that contain all the cloud from Herschel’s viewpoint. The amount of ingredients to make solar systems like our own.
    [Show full text]
  • Physical Properties of the Gas and Dust in the Orion B Molecular Cloud (L 1630)
    Physical Properties of the Gas and Dust in the Orion B Molecular Cloud (L 1630) Ralf Launhardt Astrophysical Institute and University Observatory, Schillerg¨asschen 2-3, D–07745 Jena, Germany; [email protected] and Elizabeth A. Lada Department of Astronomy, University of Florida, Gainesville, FL 32611-2055, USA Abstract. In this chapter, the distribution of dense gas and dust in the Orion B (L1630) Giant Molecular Cloud is discussed. Recent observational knowl- edge on the incidence, distribution, and properties of dense cores and pro- tostellar condensations is reviewed. In particular, the relation between cloud clumps, dense cores, dust condensations, and star formation is an- alyzed. The discussion is mainly based on recent CS multi-transition studies and observations of the thermal mm dust continuum emission. 1. Introduction Understanding the process of star formation is closely related to understanding the structure and evolution of the parental molecular clouds. Recent studies have shown that – contrary to low-mass stars, which also form in small molecular clouds (dark cloud complexes and globules) – high-mass stars form exclusively 5 in Giant Molecular Clouds (GMCs, Mcloud ∼> 10 M⊙) (see Shu et al. 1987, and Blitz 1993 for recent reviews of GMC properties). There are currently two different general views of molecular cloud structure. One is that molecular clouds are fractal with no preferred length scale (e.g., Falgarone et al. 1991; Elmegreen & Falgarone 1996). The alternative view is that GMCs are built up of “clumps” on a preferred length scale of a few parsec which is determined by the forces of gravity, pressure, etc.
    [Show full text]
  • Images of Newborn Planets, Still Swaddled in Gas and Dust, Are Challenging Theories About How Worlds Take Shape
    PICTURES OF WORLDS TO COME Images of newborn planets, still swaddled in gas and dust, are challenging theories about how worlds take shape. BY REBECCA BOYLE ome 100,000 years ago, when Neanderthals still occupied the galaxies in miniature, with swirling arms that branch off into open arcs. caves of southern Europe, a star was born. It appeared when a The latest observations, including results announced in April and July, ball of gas collapsed and ignited within a stellar factory known have revealed planets in the process of being sculpted, with dust and gas as the Taurus Molecular Cloud. Then, leftover material began flowing onto bulbous, red-hot infant worlds2,3. to cool and coalesce around it, forming dust grains and a hazy But as the menagerie of young planetary systems grows, researchers Senvelope of gas. are struggling to square their observations with current theories on how In September 2014, some of the light from that hot young star and its our Solar System and others formed. Such ideas have been in turmoil surroundings landed inside 66 silvery parabolas perched on a plateau ever since astronomers started discovering planets around distant stars in Chile’s Atacama desert — the driest on Earth. The photons had taken — a list that now numbers in the thousands. The Solar System has rocky 450 years to make the journey. Astronomers were waiting. They were planets near the Sun and giant gas balls farther out, but the panoply of conducting a test of the Atacama Large Millimeter/submillimeter Array exoplanets obeys no tidy patterns. And the rule book for world-building (ALMA), which features radio antennas separated by distances of up to is getting more complicated as researchers find evidence of planets in the 15 kilometres.
    [Show full text]